Why don’t airplanes ‘power back’ from the gate?

Question: A captain told me they discontinued “power backs” for safety reasons, i.e., pilots couldn’t see behind the plane and the brakes only stopped forward motion.

– John Clymer, Burke, Virginia

Answer: In the 1980s, airliners with aft-mounted engines ( DC-9, MD-80 and B727) used powerback to reduce the number of ground personnel. Today, most large airliners have underwing-mounted engines; they are too close to the ground and have a potential to ingest debris during a powerback.

Your comment about the brakes is not accurate. They will stop the main wheels in either direction; however, applying the brakes when backing up has the potential to stand the airplane on its tail. Powerback has safety risks; only a few aft-mounted engine jets could do it. I do not know of any airline using that procedure today.

Q: When larger airplanes taxi, are the wheels driven? Or are they powered solely by the engines?

– Douglas Chambers, Roseville, Michigan

A: When taxiing, all airplanes are powered solely by the engines.

Q: I would like to know whether one of the engines of a plane can be shut off and restarted while the plane is at high altitude. Does this cause any problems”

– SastryKVK, India

A: Yes, it is possible to shut down and restart engines during flight. The airplane is slightly more challenging to fly due to the asymmetry of the thrust, but pilots train regularly for this condition. Otherwise one engine can safely power the aircraft and all of the systems. The cruise altitude may be lower.

John Cox is a retired airline captain with US Airways and runs his own aviation safety consulting company, Safety Operating Systems.